Nickel(II) and iron(II) complexes of 4-(Pyridin-2-yl)thiazole: Spectral, magnetic and structural studies

Abstract

Iron(II) and nickel(II) complexes of 4-(pyridin-2-yl)thiazole (L) have been prepared. The electronic spectrum of [NiL₃] [ClO₂,]₂ is similar to that of the corresponding complex of 2,2'-bipyridine (bpy) but indicates that the thiazole provides the weaker field, the actual value of Dq(Ni²⁺) being within the range which suggests the likely appearance of a spin transition in iron(III). The iron(II) complexes [FeL₃] X₂ (X = ClO₄, BF₄) are, however, low-spin both in the solid state and in solution. The structure of [NiL₃] [ClO₄]₂.3H₂O has been determined, and this reveals a close similarity in the coordination environment to that in [Ni(bpy),] SO₄.7.5H₂O. The compound is monoclinic, space group P2₁/c, with four molecules in a unit cell of dimensions a 9.404(4), b 29.169(8), c 17.900(8)ź, β 137.76(1)º. The disordered structure was refined to a residual R 0.087 for 2307 observed reflections. The pseudo-symmetric ligands are orientationally disordered and one anion was also disordered. Restrained refinement with 194 parameters for 85 atomic positions produced a reliable geometry. The ligands function as bidentates, giving the cation a distorted octahedral structure.